Tuesday, July 30, 2013

Material World

This month I have mainly been testing glaze materials and porcelain clay bodies:

Every colourant, opacifier, some fritts, ashes, salts, ochers,engobes and some unknown glazes from my lab. This is what they look like before they've been fired

The shelf on the right contains materials collected from potters past, some I won't bother testing because there's not enough to be worthwhile, but I do like the eclectic collection of glass jars and materials.

Some of the materials from the shelf that I will be testing including a bag of 'Sunset Orange'. Looks like something from the 1950's.  The large bag of Smith & Smith glaze turned out to be a nice old school oatmeal glaze.

Side-handled teapot, teabowl and small breakfast bowl, along with some porcelain beakers from a recent firing. Glazed in celadon.

Cutting some shelves to size for the small kiln from old broken shelves discarded from an old pottery studio

All that remains of one of the bags of materials, I could just make out things like 'nepheline syenite' and 'kentucky ball clay'

Shrinkage and warpage bars after firing 1300 degrees C. The shrinkage bars were all under 15% shrinkage, made from throwing-consistency clay. The warpage bars all warped except the pipe clay. It was surprising that the commercial stoneware clays warped about the same amount as my own homemade stoneware and porcelain clay bodies.

These are some recently acquired materials that had been left in unlabelled bags. To get a better idea of what they all were, I had to fire a small amount of each one to see how each one reacted at 1300 degrees C. They all looked like white/grey powder but fell into four main categories: Nepheline Syenite, Silica, Kaolin and Ball Clay.

The main materials for clay bodies and glazes eg: silica, clays, fluxes, calcium carbonates, feldpars, fritts, etc.

These are the main colourants after firing to 1300 degrees. I added a strip of clear glaze down the left side of each example. Some of the colours burnt out at this high temperature but others didn't look too bad.

Unnamed materials test results. 1. is unknown pink stuff from Glenfalloch Pottery,  fired to an opaque white glaze, most closely resembling the Zircon Fritt, which you can see in the picture below. The Zircon Fritt was resourced from a retired potter. I haven't had any experience with these materials, as this is the first time they've been tested. 2 looks like Nepheline Syenite and 3 Silica.  7 is Kaolin.

Zircon Fritt is top left, pink stuff second from bottom right

Homemade porcelain clay. Throws well, vitrified with a good glaze fit. Glazed in my own clear glaze with no crazing. Not bad for a first attempt at porcelain, very simple, compared to the literature I've read that made it sound so complicated, ie, porcelain being not very plastic for throwing, prone to warping, 'glaze shivering' etc. etc. etc....

Kitten in a terracotta pot:  'My Cat Likes to Hide in Potses'

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